Reducing youth suicide has been named as a national priority for more than a decade, yet rates of youth suicide and suicide attempts have not declined. Suicide is still the 3rd leading cause of death for ages 10 - 24, and suicide rates i rural communities are more than double the national average. The public health impact of commonly applied strategies, such as gatekeeper training, is limited by minimal communication between adolescents and adults, minimal help seeking by adolescents, and by problems with accessibility and acceptability of mental health services. These barriers are particularly relevant in rural and underserved communities, which have 2-10 times higher youth suicide rates and lower utilization of available services. School-based, population oriented strategies overcome some of these limitations, but existing programs have yet to harness mobile communication devices to reach adolescents with preventive interventions directly, even beyond the school context. Text messaging is low-cost, effective tool for changing health behaviors, and is emerging as a powerful public health tool for influencing adolescent risk behavior. My application would be the first extension of mobile devices into population-based suicide prevention. The K23 career development award will provide me with the education and experience I need to become an independent investigator focused on developing and testing mobile-mediated public health interventions to reduce youth suicide. This proposal has three career development goals: Goal 1. Intervention Development. Learn the principles and practices needed to develop a safe, engaging, and effective mobile-mediated mental health intervention to target suicide risk and protective processes for youth. Goal 2. Prevention Trial Design. Gain expertise and collaborators to select and sequence prevention trial designs and research methods that are suitable for testing flexible electronically-delivered interventions for youth. Gol 3. mHealth Knowledge. Gain scientific and technical knowledge to collaborate effectively with technical experts and to assess opportunities for mHealth technologies in youth suicide prevention. I developed a research project that provides a framework for meeting these career development goals. My research objective is to develop and test the effects of a suicide preventive intervention delivered to adolescents via mobile technology. To achieve this objective my project has three aims: Aim 1. Development. Develop a safe and engaging text messaging intervention (Text4Strength) to strengthen adolescent's emotion self-regulation skills and resources. Aim 2. Field Testing. Assess the usage, usability, participant perceptions, and system operation of Text4Strength by conducting a field test of with 43 adolescents, and revise the intervention as needed. Aim 3. Pilot RCT. Assess the promise of Text4Strength. Assess the impact of Text4Strength on key proximate targets examining: skills in monitoring emotions, reducing escalation, and using adult relational resources to maintain emotional equilibrium. Secondarily, I will explore the intervention's impact on psychological distress, depressive symptoms, anxiety symptoms, and suicide ideation. The career development plan anchored by this research project will give me the skills, experiences, collaborators, and technical infrastructure that I need to be a leading expert in applying mobile technology to prevent youth suicide in rural communities. By putting an option-rich intervention in the hands of youth in rural communities, the proposed research addresses NIMH priorities: Strategic Objective 3 to improve and personalize mental health interventions; Strategy 4.1 to test novel models and methods to bring mental health interventions to diverse groups, including rural communities.